Process for sterilization of spices and leafy herbs

ABSTRACT

To avoid loss of volatile oils or cause change of color or excessive loss of moisture in raw vegetable product such as herbs or spices, the product is sterilized for human consumption by placing the product in a jacketed container where the temperature of the interior of walls of the container is elevated to approximately the sterilizing temperature, the product is then charged to the interior of the container and sterilizing, culinary steam is injected for up to five minutes; thereafter, the product is cooled and then the container pressurized to eject the cooled product for subsequent handling such as packaging; the apparatus includes two connected vessels, the first vessel being utilized to sterilize the product and the second vessel being utilized to cool and dry the product; transfer between the two vessels of the container system is effected by maintaining a pressure differential therebetween.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a process and apparatus for sterilizingraw vegetable products and, more specifically, for sterilizing dry herbsas well as spices to render them suitable for human consumption.

In the past, sterilization of agricultural food products of the typethat are packaged and placed on shelves without any significant cookingor preservatives added has depended on the use of chemicals to killbacteria that have accumulated and grown on or near the surface of thevegetable matter. Other processes have resorted to the use of moreconventional steam treatments. The difficulty with the former of thesepractices is that the chemicals used have often left a residue that isundesirable or may in fact be environmentally hazardous when disposedof. One such chemical that has been widely employed is ethylene oxidebut which has been suspected of being harmful at some concentrations. Onthe other hand, the steam processes have often resulted in significantlosses in terms of the flavor of the product being treated orunacceptable changes in the appearance such as the color of a foodproduct or in the moisture content thereof. Certain food products suchas leafy herbs and certain spices are particularly susceptible to damagewhen subjected to the steam sterilizing processes of the prior art suchas that disclosed in U.S. Pat. No. 1,061,443, granted May 13, 1913. Inother processes, such as that represented by U.S. Pat. No. 4,255,459 ofMar. 10, 1981, the food product is treated at such high temperaturesover extended periods, that there is little possibility for avoidingsubstantial losses of the volatile oils that contribute significantly tothe taste and therefore the saleability of the product.

In other arrangements, such as that disclosed in U.S. Pat. No.4,210,678, substantial physical manipulation, such as grinding andcrushing, is employed, which essentially change the nature of theproduct not to mention its appearance and taste so that the naturalappearance and taste of the product is substantially if not entirelylost.

Apparatus for sterilization of material for human use or consumption arecommercially available and can be modified to be usable in the processand system of the present invention. See, for example, U.S. Pat.4,062,646.

Other processes have consumed considerable amount of time to completethe processing of a selected quantity of raw vegetable material, thusrendering the processes substantially uneconomical, while otherprocesses have not resulted in sufficient reduction in bacteria countsto render the product suitable for safe human consumption. This isparticularly important where the product must have a sufficiently longshelf life.

The present invention overcomes the foregoing difficulties by providingan environmentally safe yet highly economical and efficient process forhandling raw vegetable material such as spices and leafy herbs withoutsacrificing the appearance, flavor level or control of moisture contentof the herbs while providing significant enhanced microbe reduction sothat the product will be suitable for packaging and storage in a retailoutlet.

In a preferred embodiment, the present invention provides a sterilizingprocess where the raw and at least superficially cleaned vegetableproduct is disposed in a first preheated container. Culinary, that issubstantially clean, steam without conventional additives is injectedinto the container while the contents are being mixed for a brief periodof no more than five minutes for a selected quantity. The stirring ormixing of the contents of the container during the injection of thesterilizing steam assists in shortening this sterilization process thusavoiding undue exposure to the sterilizing steam and/or heat which canproduce the harmful results in terms of reduction of the volatile oils,moisture content and adverse effects on the appearance of the product.This is particularly important in the case of leafy herbs which are tobe subsequently packaged without any significant treatment for sale tothe ultimate customer, either in bulk or in smaller retail salecontainers. As is well known, leaf type herbs and spices, such as bayleaves, thyme, basil, marjoram, oregano, sage and parsley, are sensitiveto temperature changes and moisture differences. The product may be heldin the first container for a selected time before being transferred to asecond container which is being maintained at a low pressure and theinterior of which is cooled by a cooling jacket. When the productreaches the selected temperatures in the second container, the productis discharged therefrom under fluid pressure admitted to the secondcontainer.

The apparatus and method of the present invention will not only provideextremely close control of the operating parameters used in thesterilizing process but also will achieve high production output andhigh energy savings.

The foregoing and other advantages will become apparent as considerationis given to the following detailed description taken in conjunction withthe accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the apparatus used in carrying outthe method of the present invention; and

FIG. 2 is a more detailed view of one of the vessels of the containersystem of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein like numerals designatecorresponding parts throughout the several views, there is shown in FIG.1 the container system 10 of the present invention. In a preferredembodiment, the system will include two cylindrical vessels 12 and 22,each of which is substantially surrounded with an outer shell or jacket14 and 24, respectively. Vessel 12 is the sterilizer vessel while vessel22 is the cooling vessel. As described in more detail in connection withFIG. 2, each vessel is provided with an axially extending shaft which isrotatable and on which are mounted paddles for agitating and mixing thecontents of each vessel. Each vessel is preferably made of stainlesssteel and is constructed to withstand high pressurization of thecontents. Each vessel 12, 24 has its interior connected through suitableconduits to a vacuum system which may include a receiving tank 26 which,in turn, is connected to a vacuum pump 28, both of conventionalconstruction. The valving and flow control devices and drains for thevarious gases and liquids that are passed through the container system10 are well known to those skilled in this art and are omitted from thedrawings for the sake of clarity. In this regard, the vacuum system willbe connected to the interiors of the vessels 12 and 22 through suitablecontrol devices and which may include program operated valves 30 whichare located in conduits connected to the inlets 16 and 17 for therespective vessels 12 and 24. From the description that follows, it willbe apparent to those skilled in the art that the entire sterilizationprocess from the loading of the vegetable product into the first vessel12 to its discharge from the second vessel 22, as well as every phase ofits treatment, can be efficiently conducted by means of a computer toobtain the most efficient, qualitative and quantitative results.

The jacket 14 of the vessel 12 is connected through suitable conduits toa steam source 15 and boiler 13 and the jacket 24 of vessel 22 may alsobe connected to a cooling fluid source 23. The interior of the vessel 12is also connected through conduit 34 to a culinary steam source 15.Regarding the term "culinary steam", it will be understood by thoseskilled in this art, that the liquid employed to generate the steam willbe potable water to reduce any possibility of contaminating or alteringthe vegetable product being handled.

Vessel 12 has a discharge port 38 leading to a remotely controlablevalve 18 which, in turn, leads to a conduit 20, the opposite end ofwhich dumps into the interior of vessel 22. Vessel 22 is also connectedthrough a control port 17 to the vacuum source 26 and vacuum pump 28. Inaddition, the jacket 24 is connected to the source of cooling fluid 23which is connected to a conventional fluid pump 25 and a chiller 29.Port 44 of vessel 22 is also provided with a remotely controllable valve46 leading in the discharge outlet 48 beneath which is a receptacle 27for receiving the discharge.

Referring now to FIG. 2, there is shown in somewhat more detail anelevational view, partly in section of the vessel 12 of the presentinvention which is similar to vessel 22, 24. The interior of the innercylinder 12 is provided with an axially extending shaft 52, which isrotatably mounted by any suitable means such as sealed bearings 54. Theshaft 52 is driven by a variable speed drive 56 such as a conventionalelectric moor. An array of paddles, one of which is indicated at 58,each being mounted to extend radially from the shaft 52 outwardly toadjacent the interior surface of the vessel 12 so that upon rotation ofthe shaft 52, material deposited within the vessel 12 will becontinuously moved by the action of the paddles 58 into and out ofengagement with the wall of the vessel 12.

Also schematically illustrated in FIG. 2, an airlock type loadingarrangement 60 is provided which includes a portable hopper or tote 62having a discharge outlet 64 which, preferably, is sealingly engageablewith a flange 66 for the inlet to the vessel 12. With this arrangement,where the interior of the vessel 12 has been preconditioned for handlinga specific vegetable product, the admission of the product to theinterior of the vessel 12 can be effected without materially disturbingthe pressure and temperature conditions set for the interior of thevessel 12. The loading valve 18 and discharge outlet 20 are eachprovided with remotely controllable rotary ball valves 18, ofconventional construction, to facilitate rapid charging and evacuationof the interior of the vessel 12. The vessel 22 is provided with anidentical discharge ball valve 46, as previously noted.

Prior to initiation of the sterilizing cycle, the hopper 62 will beloaded at a separate station indicated schematically at 70 and which mayinclude a supply source 72 for feeding the product through cleaningand/or weighing devices to the hopper 62.

The steps of the process of the present invention utilizing theforegoing apparatus will now be described.

According to a preferred method, the walls of the first vessel 12 aswell as its interior temperature are preconditioned by supplying heat tothe jacket 14 preferably in the form of steam from source 15. This willprevent condensation of the sterilizing steam upon its introduction intovessel 12. In addition, a negative pressure is applied to the interiorof the vessel 12 to an extent sufficient to rapidly move the charge ofvegetable product, such as leafy herbs in cut or uncut form and at roomor ambient temperature (about 70° F.), from the hopper 62 once theimmediately subjacent ball valve 18 is opened.

With the vessel 12 preheated, as noted above, preferably so that thewalls thereof are substantially at or above the temperature of thesterilizing steam originating with the boiler 13, and preferably with avacuum existing in the second vessel 22, ball valve 18 will be opened topermit the pressure differential existing between the closed hopper 62and the interior of the vessel 12 to pull the charge of the vegetableproduct into the vessel 12. Prior to the entrance of the vegetableproduct into the vessel 12, the paddles 58 will have been set inrotation at a predetermined rpm sufficient to effect distribution andadequate mixing of the material. Up to the present time, the lower ballvalve 18 in conduit 20 will remain closed.

Once charged, the vessel 12 is then sealed by closing the valve 18 ininlet passage 16. Movement of the valve 18 in passage 16 can be employedto produce a signal to valve controls for the sterilizing steam in line34. Sterilizing steam will then be injected for a limited amount oftime, preferably from about 10 seconds up to five minutes, and at apressure of 5 psi up to 50 psi, into the interior of the vessel 12 whilethe material therein is being mixed and agitated by the rotating paddles58. The rotation of the paddles 58 during the injection of thesterilizing steam will assure substantially more even exposure of thevegetable product in the vessel 12 to the sterilizing steam, thusaffording an appreciable shortening of the period during which steammust be injected into the vessel 12.

It will be appreciated by those skilled in the art that the precisetemperature of the steam and length of injection thereof into the vessel12 will depend on characteristics of the vegetable product beingtreated. For example, where the herb or spice being sterilized is goingto be subsequently used in another cooking process, a somewhat lowereffective sterilization, for bacteriocidal activity may be required, asopposed to the situation where the sterilized vegetable product isintended for packaging for an end user. Also, the reaction of variousvegetable products in terms of sterilization, retention of volatile oiland appearance, will vary from one plant specie to another, so that atrial and error testing of samples of the specific material to besterilized will be necessary. Use of the method and apparatus of thepresent invention, however, will permit standardization of treatment oflarge lots or batches of organic material originating from known sourcesand treated under previously known conditions.

Returning to the process, once the desired limit for sterilization hasbeen achieved, transfer of the product to the second vessel 22 iseffected. With the apparatus of the present invention, as previouslynoted, the interior vessel 22 will be set at a lower pressure as aresult of being exposed to the vacuum system through port 17 than thepressure in vessel 12. Thus, transfer is simply effected by opening thevalve 18 in the outlet passage 20, preferably while continuing rotationof the paddles 58. The interior of vessel 22 is preferably at asignificantly lower temperature due to the passage of chilled waterthrough its jacket 24 so that rapid cooling of the transfer vegetableproduct is effected. Of course, the valve leading to the discharge port17 will be closed upon opening of the discharge valve 18 and conduit 20so that pressure equalization between the two vessels will occur uponopening of the discharge valve 18 and conduit 20. Temperature sensorswill of course be provided to detect the temperature in each of thejackets and the interior of each of the vessels 12 and 22. When thetemperature sensor for the vessel 22 reflects that the product thereinhas achieved the desired temperature, the product can be dischargedthrough valve 46 to discharge outlet 48. The operation of valve 46 maybe remotely controlled by a signal derived from the temperature sensorresponsive to the temperature of the product in vessel 22. Discharge isassisted with a purified compressed gas tank 74 which is suppliedpreferably from an inert gas source 76 through a bacterial filter 78.Nitrogen gas or filtered air is preferred at a slight positive pressureof approximately 1 psig.

With the apparatus of the present invention and the method as describedabove, it will be apparent that the sterilization of a batch ofvegetable product can be carried out in vessel 12 while cooling anddischarge of a preceding batch can be effected in vessel 22.

Due to the fact that the product is exposed for only a very brief timeto high pressure and a sterilizing temperature in vessel 12 in a closedsystem, a large percentage of the volatile oils of herbs and spices willbe retained which would be otherwise lost in a continuous open process.Further, precise control of the sterilization and transport parametersassures control of appropriate moisture levels in the product which isimportant to the overall appearance of the product at the end of thecycle.

Having described the invention, it will be apparent that variousmodifications thereto may be made without departing from the spirit andscope of this invention as defined in the appended claims.

What is claimed is:
 1. The method of sterilizing raw vegetable productso as to reduce loss of volatile oils from the vegetable productcomprising the steps ofpreheating the interior of a closed containersystem of the type having jacket means to a selected temperature byintroducing a heating fluid into said jacket means to effect saidpreheating as well as maintaining the selected temperature, loading aselected quantity of the vegetable product into the container system,continuously agitating the contents of the container system at leastwhile the vegetable product is present in the container system,injecting sterilizing steam into the container system for a time periodof from ten seconds to five minutes while continuously mixing theproduct in the container system with the pressure in said containersystem being controlled to be within the range of 5 to 50 psig to reducethe bacteria present in or on the product to an acceptable level and toretain volatile oils in the product, then cooling the product andreducing the moisture on the product in the container system, thenintroducing a substantially bacteria free gas and then evacuating thecontents of the container system.
 2. The method as claimed in claim 1including exposing the vegetable product to dry heat for a duration noshorter than approximately ten seconds.
 3. The method as claimed inclaim 1 wherein the evacuation of the container system is effected withthe gas at a pressure above atmospheric pressure exterior to thecontainer system.
 4. The method as claimed in claim 1 wherein the stepof preheating the interior of the container system including passingsteam to the jacket for a time sufficient to raise the temperature ofthe interior of the container system to substantially the temperature atwhich the sterilizing steam is injected into the interior of thecontainer system.
 5. The method as claimed in claim 1 wherein the stepof introducing the gas includes introducing inert gas to raise thepressure in the container system to approximately one psig.
 6. Themethod as claimed in claim 1 including the step of, after the step ofinjecting the sterilizing steam, lowering the pressure in the containersystem to below atmospheric to assist in cooling the product andreducing the moisture on the product and then raising the pressure inthe container system by the introduction of said substantiallybacteria-free gas.
 7. A method of sterilizing raw vegetable product toreduce loss of volatile material from the vegetable product comprisingthe steps of:preheating the interior of a closed container system to aselected temperature, loading a selected quantity of the vegetableproduct into the container system, injecting sterilizing steam into thecontainer system for a time period sufficient to reduce the bacteriapresent in or on the product to an acceptable level, then lowering thepressure in the container system to below atmospheric while cooling theproduct in the container system while maintaining said container systemin a closed condition isolated from the external atmosphere, thenraising the pressure in the container system by introducing asubstantially bacteria-free gas and then evacuating the contents of thecontainer system: said container system being of the type having atleast two vessels for containing the product and the method includingthe step of feeding the product through a first one of said vessels forthe preheating and sterilizing steps and maintaining pressure differencebetween said two vessels to assist in feeding the product through thesecond one of said two vessels for the remaining steps of the method,which remaining steps include the steps of conveying the product fromsaid first vessel to said second vessel and reducing the pressure in thesecond vessel to below atmospheric to effect said cooling and thenraising the pressure in the container system by the introduction of thesaid substantially bacteria-free gas and then evacuating the contents ofsaid second vessel.
 8. The method as claimed in claim 7 wherein the stepof feeding the product to the second one of said two vessels includesthe step of feeding the product through a closed conduit means.
 9. Themethod as claimed in claim 7 further including the step of imposing apressure differential between the said two vessels wherein the pressurein the second vessel is lower than the pressure in the first vessel tothereby assist in the feeding of the product from the first to thesecond vessel.
 10. The method as claimed in claim 7 wherein the secondvessel is of the type having jacket means and the method includes thestep of cooling the interior of said second vessel by passing coolingfluid through said jacket means.
 11. The method as claimed in claim 10wherein said second vessel is provided with means for agitating thecontents thereof and the method includes the step of agitating theproduct while cooling the interior of said second vessel.
 12. The methodas claimed in claim 12 wherein said means for agitating comprises mixingpaddles mounted on shaft means rotatably mounted generally axially ofsaid second vessel so that the paddles upon rotation of said shaft willmove the product into contact with the interior wall of said secondvessel.
 13. A method of sterilizing raw vegetable product withoutsubstantial loss of volatile oils or substantial change of color orlowering of moisture content with the use of a container system of thetype having a first vessel including jacket means and mixing meansrotatably mounted on the interior of said first vessel, a second vesselincluding jacket means and mixing means rotatably mounted on theinterior of said second vessel, conduit means connecting the interiorsof said vessel with one another through valve means and means forconditioning the atmosphere in each of said vessels, comprising thesteps of:a. preheating the interior of said first vessel by passingsteam through said jacket means thereof until the temperature of theinterior of said first vessel is at a temperature no less than that ofthe sterilizing steam to be used; b. loading a selected quantity of theproduct into said first vessel without significantly altering thetemperature of the interior of said first vessel; c. injectingsterilizing steam into the interior of said first vessel for a period offrom ten seconds to five minutes while continuously mixing the productin said first vessel with the pressure in said first vessel beingcontrolled to be within the range of 5 to 50 psig; d. creating apressure differential between said first vessel and said second vesselwith the pressure in said second vessel being lower than that in saidfirst vessel; e. feeding said product from said first vessel throughsaid valve means and said conduit means to said second vessel, theinterior temperature of which has been lowered to approximately thefinal desired temperature of the product, by means of said pressuredifferential; f. cooling the product in said second vessel; and g.discharging the product from said second vessel.